Antarctic Microbes Handle Mars-Like Conditions

Lab experiments with primitive microbes taken from an
Antarctic lake have shown that the hardy single-celled organisms can tolerate
at least the warmest of the frigid temperatures found on Mars.

And they found that these species of microorganisms
"huddled" together in colder temperatures to form a chemically linked
unit called a biofilm. The finding marks the first time this phenomenon has
been detected in the Antarctic species of so-called extremophiles.

The findings provide more evidence for the ideas that liquid
found beneath Mars' surface could harbor microbial life and that life could exist elsewhere in the solar system and galaxy, which is generally incredibly
cold.

Hardy creatures

Scientists with the Maryland Astrobiology Consortium focused
on two species of cold-adapted microbes. One, called Halorubrum lacusprofundi,
is highly salt-tolerant. The other, Methanococcoides burtonii, can
live without oxygen and thrives on methane. (H. lacusprofundi is a type
of microbe that was discovered first in spoiled foods that had been salted for
preservation).

Both microbes are types of Archaea,
one of the three major types of life along with Bacteria (another class of
microbes) and Eukaryotes (a group that includes animals, plants, fungi and Protists,
e.g. paramecium, algae, protozoa and slime molds). Archaea might be able to
survive in many places in the universe beyond Earth, including some of the more
than 180 extrasolar
planets detected in the past decade, or on their terrestrial moons.

The team, led by Shiladitya DasSarma
of the University of Maryland Biotechnology Institute, part of the consortium,
grew the microbes and found they survived and reproduced at 30 and 28 degrees
Fahrenheit (about -1 and -2 degrees Celsius), respectively, just below the
freezing point of water.

"We have extended the lower
temperature limits for these species by several degrees," DasSarma said.
"We had a limited amount of time to grow the organisms in culture, on the
order of months. If we could extend the growth time, I think we could lower the
temperatures at which they can survive even more."

Slow it down

The cold temperatures of space
could result in very slow growth, with generation times possibly longer than
the average human
lifespan, DasSarma said, and this forces a reconsideration of the duration
of astrobiology laboratory experiments. "For example, is it living if one
takes a century to replicate or divide?" he said.

H. lacusprofundi was chosen
for the experiments because they could possibly thrive in the salty water
thought to exist below Mars' surface, which can remain liquid at temperatures
well below 32 degrees Fahrenheit. M. burtonnii was chosen because it
could survive on a planet lacking oxygen, such as Mars.

The lab-grown archaea also
adapted to the cold by aggregating to form biofilms or microbial mats, like the
slimy plaque that accumulates on your teeth. Aggregating to form a mat or biofilm
allows microbes to share nutrients and genetic material.

"The cold-adapted
microorganisms studied in this investigation have not been observed to form biofilms
in the past, and so the observation of biofilms
in the cold was a surprise," DasSarma told SPACE.com.

The genomes for these two
species of archaea have already been partially sequenced. Their full sequences
will soon be available, allowing scientists to learn which genes generate
proteins, such as cold-shock proteins, that help the microbes adapt to extreme
cold.

The findings were published
online in the International Journal of Astrobiology.